           [unit (take arg (injection-rate-seq unit))])
         (keyword? arg)
         (repeatedly (fn [] (typical-injection-rate arg)))))
-
-(defn rand-proppant-concentration-unit []
-  (rand-nth [:lb-per-gal :lb/gal :kg-per-m3 :kg/m3]))
 
 (defn typical-proppant-concentration
   ([]

                   [:m :ft] #(/ (* % 100) 30.48)}]
    (converter [from to])))

(defn rand-pressure-unit []
  (rand-nth [:psi :kPa :MPa]))

(defn typical-monitor-pressure
  ([units]

        (keyword? arg)
        (repeatedly (fn [] (typical-surface-treating-pressure arg)))))

(defn typical-injection-rate
  ([]
   (let [unit (rand-injection-rate-unit)]
